Neutered male siblings

Question
Just got my two male kittens neutered today and now they hiss and growl at
eachother as if they never knew one another.  Prior to today they were loving,
playful brothers.  Is this an effect of the anesthesia and will they ever remember
eachother?

Answer
Daniel,

That is common, and perfectly normal behavior for cats coming home from being fixed or going to the vet.

Cats go by smell and not by sight in recognizing other cats (with humans, they go by voice...not by sight). Your neutered cats brought home MANY different smells from the vet: anesthetic, medicinal smells, and smells of other cats...all clinging to their fur and skin so they think each other is another cat because they don't smell like they used to.

As the cats groom themselves they will be replacing their regular scent. You can keep them separated if you want until the smells are gone from their fur. It will take a few days.

A trick that I've heard a lot of people use in that situation (though I have never tried it) is to put a small drop of vanilla on each cat's forehead so they smell the same.

They also can be hissing and growling at each because they hurt from the surgery and are blaming each other for it.

They will be back to normal soon. And you are a responsible pet owner for getting them fixed!

Tabbi